


Begin Again

by Aerugonian



Series: MP100 Portal AU [1]
Category: Portal (Video Game), モブサイコ100 | Mob Psycho 100
Genre: Alternate Universe - Portal (Video Game) Fusion, Angst, Crossovers & Fandom Fusions, Found Family, Gen, MP100 characters in the Portal Universe, POV Serizawa Katsuya, Pre-Slash
Language: English
Status: Completed
Published: 2020-03-01
Updated: 2020-03-01
Packaged: 2021-02-28 01:34:32
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,798
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/22961758
Author URL: https://archiveofourown.org/users/Aerugonian/pseuds/Aerugonian
Summary: "Why do you have a clip on your arm?" Shigeo questions. His fingers reach up and tug inquisitively on the rusted metal tab welded onto Serizawa's left shield, the plastic worn off long ago. Bits of dust and dirt crumble to the ground as the wire grates with its first movement in decades.An internal system alarm activates at the physical contact, like it does every time someone touches him. Serizawa dismisses it immediately and tilts his panel a little lower so Shigeo can reach it more easily, mulling over his answer for a few seconds longer than he strictly needs to.---A Portal AU in which Serizawa is a military android, Reigen is a potato battery, and Shigeo is the rogue test subject they're helping escape.
Relationships: Kageyama "Mob" Shigeo & Reigen Arataka, Kageyama "Mob" Shigeo & Serizawa Katsuya, Reigen Arataka/Serizawa Katsuya
Series: MP100 Portal AU [1]
Series URL: https://archiveofourown.org/series/1650421
Comments: 22
Kudos: 141





	Begin Again

**Author's Note:**

> This is set in the MP100 Portal AU universe created by [Mob-on-main-street](https://mob-on-main-street.tumblr.com/) and her Discord server. This oneshot in particular is based off a stunning comic drawn by the lovely Drawspace ([check it out here!](https://drawspace.tumblr.com/post/190995647228/see-you-later-mob-on-main-streets-portal-au)). 
> 
> For those of you unfamiliar with this AU, here are a couple quick notes to be aware of:  
> \- The Portal cast has been replaced by MP100 characters.  
> \- Reigen was forcibly converted into a potato battery. Because he lost his memories during the conversion, he doesn't remember his name and Shigeo has started calling him Jaga-san (which roughly translates to "Mr. Potato"). He doesn't know he used to be human.  
> \- Prior knowledge of Portal and its premise will help immensely in understanding what's going on. You'll probably be lost if you know nothing about the game (sorry!).

_[ Did you know…? Robots are SMARTER than you. Robots work HARDER than you. Robots are BETTER than you. Volunteer for testing today at Aperture Laboratories. ]_

\--- 

**December 27, 2048 22:09:55**

It’s late at night, though no one would be able to tell the difference by looking at their surroundings. The overgrown ruins of Aperture Laboratories are silent in a permanent twilight haze, only broken up by the occasional room still lit by emergency power. 

Serizawa, of course, knows exactly what time it is down to the tenth of a second. Or, well, he’s reasonably certain he does. There’s always the chance sitting in a stasis-state for nearly fifty years corrupted his sense of time. He wouldn’t be able to tell the difference anymore. 

A few days ago, the thought wouldn’t have bothered him. A few days ago Serizawa had been 100% content with his conversion from human into an Aperture military bot. 

A few days ago Serizawa had been wandering the facility alone, searching for an escaped test subject who’d been illegally painting graffiti on the walls, and encountered Shigeo instead. 

He’s not sure the head AI of the labs has realized he’s gone rogue. It feels like a strong word – there’s still too much code in his programming to allow for completely unbridled rebellion – but there’s not much else he could call it when he’s been following after a seven-year-old and assisting an escape attempt instead of taking Shigeo back to the testing tracks, or confiscating the apparently sentient potato the kid has been carting around with him. There have been a lot of realizations Serizawa had been forced to face recently. 

Though Serizawa can only assign his system clock a likelihood of accuracy rating of 95%, he can confirm with an accuracy rating of 99.9% that he, Shigeo and Jaga-san have been wandering the facility far longer than recommended for children. 

Shigeo has been flagging for a while now, rubbing his eyes and seeming even more disinterested in Jaga-san’s constant stream of dialogue than usual. His portal gun is dangerously close to dragging on the ground, something Jaga-san has had no qualms griping about. Considering he’s currently stuck on the end of the gun, Serizawa can sympathize with his plight. 

“I’m about two inches away from having my skin scraped off by the floor, just in case that matters at all to you,” he calls, static crackling through his speaker. “One inch. I am now one inch away from the floor.” 

“Wouldn’t it grow back?” Shigeo says. He still raises up the gun a tiny bit.

“Wha- that is not the point! And for your information, I don’t know if it would grow back. It could be permanent. And then how would you feel? Bad, that’s how.” The gun drifts back down to the floor. “Hey, hey, hey, watch it, careful, holy SHIT! That was TOO close. Pretty sure you just took ten years off my lifespan, kid.” 

“Do potato batteries have lifespans?”

“That’s a stupid question, of course we do. Hey, come on, don’t you have, like, a pocket or something I can sit in?” 

“I have an antenna we could put you on, if you’d like,” Serizawa offers. “We should stop for the night regardless. You need to get some sleep, Shigeo.” 

“Okay,” Shigeo says. His expression is as impassive as always, but Serizawa's emotion recognition system detects a hint of relief. 

Jaga-san crows his exuberance as he’s relocated and Serizawa resigns himself to an excessive amount of talking in the near future. He doesn’t really mind. There’s something comforting about the lack of silence after so much time alone with only his thoughts to keep him company. Shigeo settles up near Serizawa, about to drift off but waking up again as something catches his attention. 

"Why do you have a clip on your arm?" Shigeo questions. His fingers reach up and tug inquisitively on the rusted metal tab welded onto Serizawa's left shield, the plastic worn off long ago. Bits of dust and dirt crumble to the ground as the wire grates with its first movement in decades. 

An internal system alarm activates at the physical contact, like it does every time someone touches him. Serizawa dismisses it immediately and tilts his panel a little lower so Shigeo can reach it more easily, mulling over his answer for a few seconds longer than he strictly needs to. 

He forgets the card reel is there most of the time. It isn't exactly useful nowadays without a human body or identity to give it a purpose. The logical part of his programming, the part that's still loyal to Aperture, thinks he should have thrown it away when it stopped serving a function. 

But the not-so-logical part of himself - the bulk of his code that's little more than a mess of programming inefficiencies and useless functions - refuses to let it go. He shouldn't care. He hadn't really known the man who'd given it to him over fifty years ago. Reigen had faded to little more than a distant memory of a bright smile and striking orange hair, there one day and gone the next. 

"A friend gave it to me," he says, "and I guess you could say it's my way of remembering him." 

... 

... 

... 

... 

**memory::playback("Reigen Arataka")**

... 

... 

_[ Aperture Laboratories. A trusted friend in science. ]_

\---

 **May 04, 1998 09:42:37**

Serizawa doesn’t want to complain. He really doesn’t. He loves his job, he loves feeling useful, and most of all, he loves feeling like his life has meaning for once in his life. 

But his arms ache from toting his fifth load of what feels like _rocks_ up six floors and he wishes, not for the first time, that they'd had a spare cart to make his job a little easier. He understands, though. It must be tough running such a huge company. Really, he's just being selfish expecting them to cater to him when they're the ones who had been so kind as to give him a job and a purpose in life. 

He doesn’t realize someone is standing in front of him until he quite literally runs into them. 

"I'm so sorry," Serizawa gasps, instinctively reaching out to steady the man he'd just rammed into and nearly dropping everything in his arms. 

He expects the guy to yell at him, or at least look annoyed by his clumsiness. Instead the man's face lights up in a blinding smile the moment he lays eyes on Serizawa. 

"Oh! I found you!" he exclaims, a bit breathlessly like he's been running. His hands fly out like he intends to take a couple of the boxes, though he falters almost immediately. After a moment of awkwardness he just pushes one of the boxes more securely into place. 

Serizawa raises his eyebrows, trying to determine if the guy is just weirdly casual with people he doesn't know or if he knows Serizawa from somewhere. He's pretty sure he's never seen this man before in his life, and he doesn't look like the type that's easily forgotten. He's a few inches shorter with conspicuous sandy-orange hair, large dark eyes framed by a pair of very stylish silver glasses. A bit sweaty, perhaps, but strikingly handsome in a hard to quantify way. 

Serizawa's stomach swoops. Just a little bit. 

The man grins crookedly and waves a very familiar identification card in the air. "You dropped your key card a few floors down," he explains. 

Serizawa's eyes widen. Now that he thinks about it, he can vaguely recall leaving it on top of one of these boxes while he'd been working out the logistics of carrying a frankly excessive number of items from one storage room to another (literally identical) one. "Thank you so much," he says. 

And then he realizes he can't actually grab it. His fingers flex around the edges of the lowest box as he debates setting them down, but it's awfully busy, and what if someone trips over it because they don't see it? What if someone trips and gets hurt and decides to sue him because he wasn't careful enough and -- 

In the end it doesn't matter, because the man is reaching out with the card without waiting for Serizawa to set anything down. "Here, let me just," he starts to say, almost setting it on top of the boxes before seemingly rethinking that decision. His hand hovers uncertainly before he steels himself and resolutely sticks it in a pocket. The tips of his fingers leave a searing, feather-light trail along Serizawa's jacket and linger just a moment too long to be completely casual. "Uh. Yeah." 

"I didn't even realize I'd dropped it," Serizawa says. He wets his lips nervously. 

Reigen takes a step back and some of the pressure in the hall dissipates with the space. He gestures animatedly as he speaks. "You were already in the elevator by the time I noticed it and picked it up. So I took the stairs to reach you -- you move fast for carrying that much, by the way. You really should be more careful." 

Serizawa winces. "I'm sorry I made you go to all that trouble." 

"No, no, it's fine! But I'd recommend a card reel for the future so you don't lose it again." Reigen tugs on his own ID card to show off the cord. "Actually, I think I have a spare one." 

"Thank you, but you don't have to do that." 

He waves a hand dismissively. "It's just collecting dust in my drawer right now. Might as well put it to better use. Just tell me what your name is and I'll drop it off at your locker." 

"I'm Serizawa. Serizawa Katsuya."

Reigen grins. "I'm Reigen Arataka. Maybe I'll see you again sometime." 

... 

... 

**memory::playback("Reigen Arataka");**

**return "end"**

... 

... 

... 

... 

**December 27, 2048 22:43:55**

A burst pipe drips steadily nearby, echoing through the vastly empty, broken space. Jaga-san is silent for once. He’s probably got an idea of how this story ended. 

"That was nice of him," Shigeo says. "Did he get turned into a robot too?" 

"No," Serizawa murmurs. He thinks his throat would feel tight, if he had one. "He died a very long time ago.” 

He never did see Reigen around again. Serizawa had found a card reel at his desk the next day with a cheerful little note and a desk number. He’d thought it could be the start of something special. Instead he’d gone to Reigen’s desk and found it being cleared off, a life cut short and promptly forgotten. No one had seemed interested in knowing what happened, and Serizawa never did find out why. 

They’d allowed him one sentimental item when he’d undergone his conversion into a mechanical body. 

He chose the card reel. 

**Author's Note:**

> No, Reigen's not actually dead, in case you didn't read the notes at the top. He's alive and "well" as an amnesiac potato battery. Yes, he eventually recovers at least part of his memories. Just not yet. 
> 
> Thank you so much for reading! Comments/kudos are always greatly appreciated - let me know what you thought! I'll probably be writing more within this AU-verse, so feel free to subscribe to the series if you're interested in seeing more in the future. 
> 
> I have a Mob Psycho 100 Tumblr @ [grandmasterreigen.](https://grandmasterreigen.tumblr.com/) Come check it out if you'd like! 
> 
> If you have further questions about the AU, feel free to ask in the comments, on my Tumblr or Mary's, or [join the Portal AU Discord server](https://discord.gg/Rnur4ZP) to see all the cool content being made for it!


End file.
